Exhaust manifold

ABSTRACT

An exhaust manifold for an internal combustion engine with an exhaust gas conducting inner tube and an outer jacket which is insulated particularly effectively and inexpensively is described. To this end, it is suggested to embody the insulation as an insulating molded part pressed into shape and to arrange it between the jacket and the interior, the insulating molded part containing an insulating fibrous tissue and a binder.

FIELD OF THE INVENTION

The invention relates to an exhaust manifold for an internal combustion engine of the type having an exhaust gas inner tube and an outer jacket.

BACKGROUND OF THE INVENTION

Exhaust manifolds are often insulated, in particular if the exhaust gas temperature is to reach a high level as soon as possible for downstream units, for example a catalyst or a turbocharger or the like, so that the downstream units can work correctly, or the construction can be built from low-quality materials, or so that these work at all.

SUMMARY OF THE INVENTION

The object underlying the invention is to provide a particularly effective kind of insulation for an exhaust manifold.

The object is achieved by the features of an insulation embodied as an insulating molded part pressed into shape and arranged between the jacket and the inner tube and that contains an insulating fibrous tissue and a binder.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows a schematic representation of a section through an exhaust manifold.

BACKGROUND OF THE INVENTION

The inventive design as an insulating molded part on the basis of an insulating fibrous tissue permits arranging the insulation inside, i.e. between the exhaust gas conducting inner tube and the outer jacket of the exhaust manifold. By this, the outer jacket is also protected from increased temperatures, or an increase in the temperature level in the exhaust gas for the downstream units is reached earlier, and some sound protection is simultaneously achieved. By the design as a molded part on the basis of a woven cloth of insulating fibers, a mechanical cohesion of the insulation is furthermore achieved without any additional provisions, for example without any additional foil coating or the like. By this, the air gap between the jacket and the inner tube provided in the installation is maintained even under rough operational conditions, and fibers are simply and safely prevented from being blown out.

Advantageous further developments of the invention can be taken or appreciated from the claims.

The insulating fibrous tissue preferably consists of silicate fibers, but it can also consist of glass fibers or the like.

The binder used for compression molding the insulating molded part is alumina, in particular bentonite.

P-2869

The insulating molded part is preferably installed such that the insulating fibrous tissue, or the side of the insulating molded part containing the largest proportion of insulating fibrous tissue, is adjacent to an air gap.

It is furthermore possible to mix the insulating molded part with pigments which have a heat absorbing or heat reflecting effect.

One embodiment of the invention will be illustrated below with reference to the single figure which shows a section through a schematically represented inventive exhaust manifold.

The FIGURE shows, in a schematic representation, a section through an exhaust manifold 1 for an internal combustion engine, preferably for motor vehicles.

The exhaust manifold 1 contains the usual exhaust gas conducting inner tubes 2 which are surrounded by a jacket 3 at a distance A. The exhaust tubes 2 and the jacket 3 can consist of the usual materials, such as cast parts or steel plate.

An inner insulation 4 is accommodated within the distance A. The inner insulation 4 preferably covers the complete inner surface of the jacket 3, however, it is thinner than the distance A, so that, despite the installation of the insulation 4, an insulating air gap 5 to the inner tube 2 remains.

The insulation 4 is between 1 mm and 3 mm, preferably between 1.5 mm to 2 mm thick, so that the air gap 5 is reduced by this amount with respect to the distance A.

The insulation 4 is embodied as an insulating molded part. The insulating molded part contains a carrier mat in the form of a woven cloth of insulating fibers, in particular silicate fibers, but also glass fibers or the like. The insulating fibrous tissues are commercially available and consist of transverse and longitudinal threads which are interlaced with most diverse kinds of weave known from the field of textiles. A particularly preferred embodiment of an insulating fibrous tissue is on the market under the trade mark Hakoterm® 1200 HG 1305. This material consists of twisted silicate fibers that have been woven to form a woven mat.

Instead of woven mats of silicate fibers, however, woven glass fibers or woven cloths of similar fibers suited for insulation, e.g. mineral fibers, can also be employed.

For the manufacture of the insulating molded part, an adequate blank of the insulating fibrous tissue is provided with a conventional binder, for example alumina in the form of bentonite, suspended in water, and then finally shaped by hot pressing.

Color pigments can also be added to the binder and influence heat absorption and/or heat reflection such that, on the one hand, the surrounding components are protected from thermal overload, and on the other hand, care is taken that, when the internal combustion engine is started, an increase in the exhaust energy is achieved very quickly, resulting in a quick increase in the temperature in the exhaust pipe during the warm-up time, and thereby in a reduction of NO_(x) values and CO₂ emission.

A particularly suited color pigment is a copper chromite black spinell, as it is available, for example, as Black 30C965 from the Company “The Shepherd Color Company”. This color pigment mainly acts in an absorbing manner. A preferably reflecting color pigment is a yellow color pigment (buff rutile on the basis of chrome, antimony and titanium), preferably YELLOW 193 of the same company.

The color pigments are preferably admixed to the binder, but they can also get onto or into the insulating molded body in any other way.

The installation of the insulating molded part 4 is effected such that the woven side of the insulating molded part, i.e. the side which consists of the woven mat or comprises the higher proportion of the woven mat, abuts the air gap 5, and the opposite side abuts the jacket 3. This ensures that maximum protection against the blowing out and detachment of components of the insulation due to vibrations or the like is provided, so that the risk of malfunctions due to blown away or otherwise displaced particles in the exhaust system is not given. The insulating molded part 4 manufactured in this manner is self-supporting, so that no additional protective layer, for example a metal foil or the like, is required as a delimitation or for mechanical stabilization. The insulating molded part 4 can be simply fixed at the outer jacket 3, and the jacket 3 can be fixed, together with the insulation 4, around the inner tubes 2 with the required air gap 5. 

1. Exhaust manifold (1) for an internal combustion engine, having an exhaust gas conducting inner tube (2), an outer jacket (3), and an insulation (4), characterized in that the insulation is embodied as an insulating molded part (4) pressed into shape and arranged between the jacket (3) and the inner tube, and that it contains an insulating fibrous tissue and a binder.
 2. Exhaust manifold according to claim 1, wherein: the insulating fibrous tissue contains a fiber mat of mineral fibers, such as a woven glass and/or silicate and/or ceramic fiber mat.
 3. Exhaust manifold according to claim 1, wherein: the binder is alumina, in particular bentonite.
 4. Exhaust manifold according to claim 1, wherein: the insulating molded part (4) is separated from the inner tube (2) by an air gap (5).
 5. Exhaust manifold according to claim 4, wherein: the insulating fibrous tissue of the insulating molded part (4) is arranged adjacent to the air gap (5).
 6. Exhaust manifold according to claim 1, wherein: the insulating molded part (4) contains heat absorbing and/or heat reflecting pigments.
 7. An exhaust manifold for an internal combustion engine comprising: an exhaust gas conducting inner tube; a jacket spaced a distance from said exhaust gas conducting inner tube; and an insulating molded part pressed into a shape and placed between said exhaust gas conducting inner tube and said jacket, said insulating molded part comprising an insulating fibrous tissue and a binder, whereby a mechanical cohesion is obtained and fibers are prevented from being blown out.
 8. An exhaust manifold for an internal combustion engine as in claim 7 wherein: said insulating molded part is placed adjacent said jacket so that an air gap is formed between said insulating molded part and said exhaust gas conducting inner tube.
 9. An exhaust manifold for an internal combustion engine as in claim 7 wherein: the insulating fibrous tissue comprises a woven cloth of insulating fibers. 